NIKE Free 4.0 V2 Running Shoes Nike Free Technology - This shoe delivers the feel of training barefoot with a natural fit and enhanced flexibility. Breathable mesh upper - A highly breathable upper also built with synthetic upper for greater durability. Fused Phylite midsole/outsole - for a super lightweight and resilient ride Strategically Placed Carbon Rubber - under high-wear areas for durability. Reflective Details - For keeping you safe in low light conditions.